At Intellisystem Technologies for home automation a solution for this we use the Z-Wave protocol. This protocol is not a wifi level, but at an 868Mhz level, and brings a device into sleep mode once it not in use. It only consumes power in use hence a battery will last for 4 -5 years. It can also sent updates to a central hub telling you if battery replacement is needed or not. It still means that battery replacement is needed once and a while, but in the end not often needed.